1. Field of the Invention
The present invention relates to a rotary connector device that electrically connects between a body of an automobile and a steering wheel.
2. Description of the Related Art
A conventional rotary connector device of this type is as shown in FIGS. 10 and 11, for example. The conventional rotary connector device 101 is mounted to a vehicle-sided combination switch 103 attached to a steering shaft. Between the rotary connector device 101 and the combination switch 103, a steering-angle sensor 105 which detects a steering angle of the steering wheel 111 is interposed for the sake of various controls of an automobile.
A pair of engagement bosses 109 are protruded at a disk 107 which is a rotation-side member of the rotary connector device 101, and are engaged with the counterparts of the steering wheel 111, and the disk 107 is conjunctively rotatable relative to the steering wheel 111.
The rotary connector device 101 and the steering-angle sensor 105 are coupled to each other by means of an engagement portion 113. The engagement portion 113 is provided independently of the disk 107, is attached to the disk 107, and extends to the steering-angle sensor 105. An engagement groove 113a is formed on an outer circumferential face of the engagement portion 113, and is engaged with a joint protrusive portion 105a which is formed on an inner circumferential face of a deceleration gear of the steering-angle sensor 105.
Therefore, when the steering wheel 111 rotates, such rotation is transmitted to the steering-angle sensor 105 via an engagement boss 109, the disk 107, the engagement groove 113a, and the joint protrusive portion 105a, and a steering angle can be detected.
However, the engagement portion 113 is attached to the disk 107, and is structured to transmit a rotation from the disk 107 to the steering-angle sensor 105 via an engagement between the engagement groove 113 and the joint protrusive portion 105a. Thus, the rotation is transmitted via three engagements between the steering wheel 111 and the disk 107; between the engagement portion 113 and the steering-angle sensor 105; and between the disk 107 and the engagement portion 113. Therefore, a large margin of error may occur to transmission of the rotary angle, due to a backlash occurring among the respective members.
Such a large margin of error emerges as an increase of a steering-angle detection error of the steering-angle sensor 105 with respect to steering of the steering wheel 111, and there has been a problem that a limitation to timely vehicle control occurs.
Patent Document 1: Japanese Laid-open Patent Application No. 2000-3640